Newly widowed, Kay McCowen quit her job, sold her house, applied for Social Security and retired to Mexico. It was a move she and her husband, Mel, had discussed before he passed away in 2012.

"I wanted to find a place where I could afford to live off my Social Security," she said. "The weather here is so perfect, and it's a beautiful place."

She is among a growing number of Americans who are retiring outside the United States. The number grew 17 percent between 2010 and 2015 and is expected to increase over the next 10 years as more baby boomers retire.

Retirees most often cite the cost of living as the reason for moving elsewhere, said Olivia S. Mitchell, director of the Pension Research Council at the University of Pennsylvania's Wharton School.

"I think that many people retire when they are in good health and they are interested in stretching their dollars and seeing the world," Mitchell said.

McCowen's rent in Ajijic, a community outside Guadalajara near Mexico's Lake Chapala, is half of what she was paying in Texas. And since the weather is moderate, utility bills are inexpensive.

In some countries, Mitchell said, retirees also may find it less expensive to hire someone to do their laundry, clean, cook and even provide long-term care than in the United States.

McCowen has a community of other American retirees nearby and has adjusted well.

But for others there are hurdles to overcome to adjust to life in a different country.

Viviana Rojas, an associate professor at the University of Texas at San Antonio, says the biggest obstacle is not speaking the language or knowing the culture.

"Many of the people we interviewed said they spoke Spanish, but they actually spoke very little Spanish," said Rojas, who is writing a book about retirees in Mexico. "They didn't have the capacity of speaking enough Spanish to meet their basic needs like going to the doctor or to the store."

Access to health care also can be a challenge. While retirees still can receive Social Security benefits, Medicare is not available to those living abroad, Mitchell said.

Joseph Roginski, 71, says that while the cost of living is higher in Japan, access to health care is not. "Things are very expensive here. It is impossible to live off Social Security alone," said Roginski, who was stationed in Japan in 1968. "But health insurance is a major factor in staying here."

The former military language and intelligence specialist said he pays $350 annually to be part of Japan's national health insurance. His policy covers 70 percent of his costs. The rest is covered by a secondary insurance program for retired military personnel.

Japan experienced the biggest growth of American retirees — at 42 percent — and more than any other country between 2010 and 2014, according to data from the Social Security Administration. The large U.S. military presence in the country may be a factor.

There are more than 50,000 U.S. military servicemen and -women stationed in Japan. The presence is so large that in the island of Okinawa, the U.S. military occupies about 19 percent of the area, according to Ellis S. Krauss, professor emeritus of Japanese politics and policy-making at the University of California, San Diego.

Roginski, who volunteers for the Misawa Air Base Retiree Activities Office, said he helps connect more than 450 retirees and their families living in Northern Japan with resources. He said he would never move back to the United States.

"We have a real strong sense of security here," he said. "I can leave my door unlocked and no one will take anything. When I go to another country I feel nervous, but when I come back I feel like I'm home."

Mexico has become home for retired firefighter, Dan Williams, 72, and his wife, Donna, 68. The couple has been living near the same retirement community in Lake Chapala for 14 years.

"The climate and the medical services are very good," Williams said.

Williams teaches painting to adults and children and puts together a monthly magazine for the local American Legion. He is also a member of the Lake Chapala Society, which offers daily activities for American retirees.

It was those same services that attracted McCowen to the region.

"Before moving, I found out how many widowed and divorced women lived here," she said. "There is comfort in numbers."

She says she loves being in a lively community.

"I see older people walking year round. I see them all over the place, even in their wheelchairs. If they were in the U.S., they would probably be in a nursing home," she said. "I don't think I could move back."